I just got a very comfortable ergonomic keyboard, but sadly it uses a proprietary wireless transceiver. With Bluetooth and old Logitech wireless keyboards, they’ve always asked me to enter a new pairing key each time. This keyboard just worked out of the box, without any pairing or configuration. Does that mean that all the keystrokes are broadcast in plaintext to anybody with the same transceiver?
Possibly, or possibly it’s been pre-paired with the receiver. Unless you work for the NSA or the Mob, though, I wouldn’t worry about it. These things are notoriously short-range.
A good question… I just did a quick search, and I found a patent from MS from 2001 . It’s old, could be a competitor to WiFi or BT. But, that did have a cryptography module.
If you can connect two keyboard to one receiver, or, one keyboard to two receivers then I would say no. It’s probably at such a low power that it would be hard to intercept readily.